The admirably bushy lip-warmer, which he sports in the new Kiwi crime series Harry, began life as part of a beard when the actor did a film called Mariah Mundi And The Midas Box in Bristol.

"I thought, 'Why don't I just take off the beard bit and leave the moustache and see if it works?' " Neill says.

"I actually did another film called The Tomb in New Orleans and I said, 'Can I keep the moustache because I'm going to do a thing called Harry in New Zealand?' and they said, 'Yeah, why not?'

"The Harry people seemed to like it so I stuck with it.

"Then I knew I had to do another cop show in England which required a moustache anyway. I did a movie called A Long Way Down, playing a conservative politician and thought I might as well keep it on for Peaky Blinders, in which I play a psychotic Belfast cop in 1919. So the moustache went the whole distance for that whole year."

The well-groomed crumb catcher is a perfect fit with his Neill character, the no-nonsense detective Jim 'Stocks' Stockton, who is mentor of the titular character detective Harry Anglesea (Oscar Kightley).

"It got a really good showing," says Sam of his moustache.

"I did give it a bit of a trim because if you're a moustache aficionado, you need to draw the line between the nose and the upper lip and keep a little bit of a clearing there so it doesn't look like it's all just tumbled out of your nose. That's not a good look."

Neill copped a fair bit of abuse from "civilians and family" for keeping the mo, but like his old-school policeman character, he stuck to his guns.

"This could turn the tide for the moustache. There was a while when it was just the preserve of the Village People and All Blacks but now it's open slather. You can do what you want.

"I cut it off for Christmas and everyone hated it. I rather disliked it too. But when it came off, I went into a decline for a couple of days. I missed it. I was in mourning for a moustache."

He describes Detective Stockton as "a tough cop, but a fair one and I think a pretty gnarly old guy".

The show is inspired by the true events that heralded the rise of methamphetamine-fuelled crime in New Zealand, including a double homicide in south Auckland in 2002.

It is the first time that Irish-born, New Zealand-based Neill, who is known for his international film and television roles, has starred in a Kiwi drama series.

Neill was happy to work again with Oscar, whom he got to know from his guest role on the cartoon bro'Town, which Oscar co-created. The two actors even share a birthday.

"It's always nice to work with friends and I hadn't seen Oscar in straight drama before. I've seen lots of Oscar's work on film, and on stage actually, but I hadn't seen him do straight drama before but he's very well equipped for it.

"Oscar has got the most expressive and malleable face which suits pretty much everything."

It was also a good chance to work at home and spend time at his vineyards in the South Island, which he says keep him busy between his many acting jobs.

He is one of the few New Zealand actors to attain international fame without having done a stint on Shortland Street. But he's not ruling it out yet.

"I was just thinking the other day, they're about to re-release Jurassic Park in 3D and when that first came out, it was 20 years ago now, and we had a premiere in Auckland and I came back for that.

"My nephews were small guys at that point - maybe eight, 10, something like that - and there was a big do, a big premiere, an enormous party afterwards.

"The next day I went around to see my brother and I wanted to know what they thought. I asked one of the nephews, 'How was last night?' and he said, 'It was really cool'. I said, 'What was cool about it?' and he said, 'I saw three people from Shortland Street there'. It is, in many ways, the pinnacle, isn't it? An ambition unrealised. I could get back from - where had Dr Ropata been? Guatemala. Back from Guatemala."WHEN: Harry, TV3 on Wednesday